Question 746009
Add their rates of draining to get their
rate of draining together
( 1 pool / 7 min ) + ( 1 pool / t min ) = ( 1 pool / 3 )
Solve for {{{ t }}}
{{{ 1/7 + 1/t = 1/3 }}}
Multiply both sides by {{{ 21t }}}
{{{ 3t + 21 = 7t }}}
{{{ 4t = 21 }}}
{{{ t = 5.25 }}}
{{{ .25*60 = 15 }}}
It will take the 2nd pump
5 min and 15 sec by itself